(1) Field of the Invention
The invention relates to a method for generating a rough surface on a polymer or a polyamide membrane for the top layer of a flexible rule, which the polymer or the polyamide membrane is utilized as the top layer covering the flexible rule to help achieve clear reading and minimizing the notorious reflection effect.
(2) Description of the Prior Art
Generally, a flexible rule is essential an extended-length strip made of slim and flexible metal sheet, where measuring readings are printed on single or double surfaces of the extended-length metal strip. In a well-finished flexible rule, surface treatment on both side of the flexible rule is necessary for protecting the readings or color on the rule surface from scratches during repeatedly rolling or bending operation of the flexible rule. Conventionally, the surface treatment for the rule surface is to apply a layer of lacquer or the like by spraying over the reading surface of the flexible rule. By providing the smooth shining layer of lacquer or the like, the reading surface then can be protected and show a lovely appearance. However, though the traditional surface treatment can provide protection on the reading surface of the rule, yet the spraying layer is sometimes too thin to provide sufficient protection for the readings from being rapidly scratched off.
To overcome the aforesaid disadvantage of conventional surface treatment, the up-to-date method is to apply a transparent layer of polymer or polyamide membrane on top of the reading surface of the flexible rule. The polymer or polyamide membrane has appreciable strength against scratch and sufficient adhesion, and so can provide better protection than the lacquer layer does.
The major purpose of applying a lacquer layer, a polymer or a polyamide membrane on the reading surface of the flexible rule is to protect the paint and the printed readings from scratch off. Nevertheless, in practice, the aforesaid layer sometimes causes vision problems in reading. It is well known that the application field of the flexible rule could be anywhere indoors or outdoors and each place might have different light intensity. In case that a shining source exists in the application field, the smooth reading surface of the flexible rule will reflect the intake light into user's eyes, and make the reading hard to tell. The reason for such a vision problem of the flexible rule under a shining circumstance is the smoothness of the lacquer layer, or the polymer or polyamide membrane on the reading surface. Under a shining source, the smooth protect layer on top will reflect most of the intake light intensity, and the reflected light will then impede the clear reading of the correct scale on the reading surface of the flexible rule.
Therefore, an invention devoting to resolving aforesaid disadvantages of the top layer on the reading surface of a flexible rule is necessary, definitely.